Method and apparatus for testing electronic devices

ABSTRACT

An apparatus including a circuit substrate having a plurality of contactor pins extending between two opposing surfaces; and at least one capacitor mounted on one of the two opposing surfaces of the circuit substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

The application is a Continuation of application Ser. No. 10/074,498 filed Feb. 11, 2002, now U.S. Pat. No. 6,597, 190, which is a Continuation-In-Part of application Ser. No. 09/675,802 filed Sep. 29, 2000 abandoned.

FIELD

This invention relates generally to testing electronic devices and, more specifically, to a device for testing semiconductor devices.

BACKGROUND

Once an electronic device is manufactured, the electronic device is generally tested to ensure that it is working property. FIG. 1 illustrates a conventional assembly used to test the performance of an electronic device 120 such as an integrated circuit chip. Assembly 100 includes handler 110, test contactor 130, loadboard 160, and tester 170. Tester 170 supports loadboard 160 and test contactor 130 in order to test electronic device 120. Loadboard 160 serves to electrically couple plurality of pins 150 to tester 170. Handler 110 carries electronic device 120 from an area such as a final test location in a manufacturing area (not shown) and holds electronic device 120 in place while set of contact points 125, such as an array of solder balls at the bottom surface of electronic device 120 contact a corresponding plurality of pins 150 that protrude from test contactor 130.

Plurality of pins 150 includes a set of power pins, a set of ground pins, and a set of signal pins. Signal pins typically carry digital I/O signals such as address bits, control bits, and/or data bits. Power pins provide voltage from a power source (not shown) to set of contact points 125 for testing the performance of electronic device 120. Ground pins generally have ground zero potential to carry the current to ground and prevent the voltage in the power pins from overheating test contactor 130. To prevent a short circuit, power pins are typically isolated from ground pins.

FIG. 2 illustrates a schematic top view of test contactor 130 on loadboard 160. Test contactor 130 includes test contactor housing 210 that surrounds plurality of pins 150. In testing, for example, set of contact points 125 of device 120 by plurality of pins 150, pins may be addressed individually at fast transient times. The nature of the quick addressing of plurality of pins 150 (e.g., power pins coupled to power rails) causes voltage noise that is generally attributable to variations in the power source (not shown). Outside of test contactor housing 210 a plurality of capacitor pads 280 that include a plurality of capacitors (e.g., fifty capacitors) are placed on loadboard 160 for minimizing variations in the external power source.

FIG. 3 illustrates a cross-sectional view of a portion of the assembly of FIG. 1 including a magnified portion of test contactor 130. Test contactor 130 includes test contactor housing 210 that supports elements of test contactor 130, namely plurality of pins 150. Test contactor housing 210 includes a bottom plate typically made of a polymeric or plastic material such as VESPEL® commercially available from E. I. Dupont de Nemours of Wilmington, Del. The combination of test contactor 130 and loadboard 160 may be referred to as test interface unit 270 that interfaces with set of contact points 125 of electronic device 120.

Test contactors have generally been unable to adequately resolve several problems associated with testing of the performance of electronic devices. Test contactors typically have high frequency noise and voltage drops in power delivery systems due, in part, to fast switching transients (e.g., pin to pin) and the current consumption associated with electronic device testing. To address the noise considerations, capacitors are added to loadboards. Unfortunately, there is a very limited and a relatively ineffective decoupling area on test loadboards for a comprehensive test tooling decoupling solution (e.g., suitable capacitance to reduce noise). Yet another problem relates to dissipation of the heat generated from plurality of pins 150.

In order to reduce the effects from these problems, modifications have been made to test contactors that affect the cost and quality of test contactors. First, the length of each pin of plurality of pins 150 in test contactor 130 has been reduced from, for example, 7.8 millimeters (mm) or greater to about 3.5 mm. However, by reducing the length of each pin, plurality of pins 150 tend to be less reliable and the cost of test contactor 130 is increased.

Second, conventional test systems use a large quantity of decoupling capacitors such as fifty capacitor on, for example, loadboards. These loadboards are generally already fully populated with pin contacts. The larger number of decoupling capacitors increases the cost of the conventional test systems.

Third, conventional test systems increase the time period in which to test the performance of an electronic device such as an integrated circuit due to factors such as excessive noise. By increasing this time period, the time to produce a functional integrated circuit is also increased. This in turn affects the overall cost of producing integrated circuits. It is therefore desirable to have an apparatus and a method for addressing these disadvantages in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements, and in which:

FIG. 1 illustrates a schematic side view of an electronic device testing assembly of the prior art;

FIG. 2 illustrates a schematic top view of the test contactor and loadboard of FIG. 1;

FIG. 3 illustrates a cross-sectional side view of a portion of the testing assembly of FIG. 1;

FIG. 4 illustrates a partial cross-sectional view of one embodiment of a testing system including a test contactor;

FIG. 5 illustrates a top perspective view of a portion of the test contactor of FIG. 4 and shows a ground plane and ground pins extending therethrough;

FIG. 6 illustrates a top perspective view of a portion of the test contactor of FIG. 4 and shows a power plane and power pins extending therethrough;

FIG. 7 illustrates an exploded perspective view of a single ground pin above a portion of a ground plane;

FIG. 8 illustrates an exploded perspective view of the ground pin of FIG. 7 coupled to the ground plane;

FIG. 9 illustrates a cross-sectional view of a ground pin extending through a power plane and coupled to a ground plane of a test contactor;

FIG. 10 illustrates a magnified top planar of a portion of the test contactor of FIG. 4 showing pins disposed through apertures;

FIG. 11 illustrates a top planar view of the test contactor of FIG. 4 showing capacitor pads about the periphery;

FIG. 12 illustrates a cross-sectional side view of a portion of the test contactor of FIG. 4 and shows capacitors located on a capacitor pad;

FIG. 13 illustrates a magnified top planar view of two capacitor pads on the test contactor of FIG. 4 in accordance with one embodiment of the invention;

FIG. 14 illustrates a flow diagram for using a test contactor on a printed circuit board in accordance with one embodiment of the invention.

DETAILED DESCRIPTION

An apparatus and technique for testing the performance of electronic devices such as circuit devices is disclosed. In one embodiment, an apparatus for testing electronic devices includes a housing such as a test contactor housing which has a plurality of test contactor pins that extend therethrough. The plurality of test contactor pins include a first set of power pins, a second set of ground pins, and a third set of signal pins. A printed circuit board (PCB), attached to the housing, has at least one first ground plane and at least one first power plane. The power pins are electrically coupled to the first power plane and the ground pins are electrically coupled to the first ground plane. The first set of power pins, the second set of ground pins, and the third set of signal pins extend through the PCB.

In one aspect, the testing apparatus decreases the cost and time required to test electronic devices and increases the quality of testing an electronic device. For example, decoupling performance is improved by the contribution from a power plane and a ground plane in the test contactor housing rather than externally located, e.g., on a loadboard. Configured in this manner, the voltage drop associated with pin addressing is also reduced.

Referring to testing aspects, decoupling performance is also improved by placing one or more capacitors, such as surface mount technology (SMT) capacitors, onto a test contactor housing that includes a PCB that results in increased physical closeness (spacing) between the capacitor(s) and the electronic device to be tested. This allows the power distribution loop area to be decreased which reduces the impedance and thus the bypass noise. Additionally, the capacitor response time is also reduced against a sudden demand of the current.

The enhanced decoupling capability due to the placement of capacitor(s) on the test contactor also decreases the number of decoupling capacitors in the test interface unit. By having fewer decoupling capacitors, the cost of the test tools such as a test interface unit and a test contactor is reduced. This also allows the test interface unit to have a greater amount of space to place additional elements in the test interface unit.

By incorporating a power plane and a ground plane into the housing of a test contactor and possibly incorporating capacitors into the test contactor housing, voltage drops in pin addressing may be reduced. Longer pins (e.g., lengths of 7.8 mm or greater) may be used that generally have greater reliability and an extended lifetime than current state-of-the-art reduced-size (e.g., 3.5 mm) pins. By using these longer pins, the cost of the test contactor may also be reduced. The reduced voltage drop also tends to speed device testing.

In the following description, numerous specific details such as specific materials, processing parameters, processing steps, etc., are set forth in order to provide a thorough understanding of the invention. One skilled in the art will recognize that these details need not be specifically adhered in order to practice the claimed invention. In other instances, well known processing steps, materials, etc., are not set forth in order not to obscure the invention.

FIG. 4 illustrates a partial cross-sectional view of testing system 300. Testing system 300 includes test contactor 305 of test contactor housing 310 and PCB 320 shown in ghost lines that may be made of a polymeric or plastic material. In this example, PCB 320 includes at least one power plane 360 and at least one ground plane 370 extending laterally (in an x-direction) through test contactor housing 310. It is appreciated, however, that PCB 320 may include a plurality of power and ground planes.

Apertures located in PCB 320 are configured to receive plurality of pins 155 that include power pins, ground pins, and signal pins. An aperture is slightly larger in diameter than the diameter of a pin in plurality of pins 155. Plurality of pins 155 generally may be longer, cheaper, and more reliable than the state-of-the-art short pins recommended for prior art test contactors. Plurality of pins 155 are coupled, where desired, respectively to power plane 360 and ground plane 370. Power plane 360 receives power from a power source (not shown) external to test contactor 305.

FIG. 5 and FIG. 6 illustrate top perspective views of test contactor 305 with the contactor body or PCB 320 removed and only a ground plane and a power plane shown in of the test contactor, respectively. FIG. 5 further shows ground pins extending therethrough with power pins shown in ghost lines. FIG. 6 reverses the view showing power pins extending through the test contactor and ground pins shown in ghost lines.

Referring to FIG. 5, ground pins 340 are disposed through PCB 320 in one embodiment and coupled to ground plane 370. One way this is accomplished is by coupling ground pin 340 to ground plane 370 as illustrated more specifically in FIG. 7 and FIG. 8. In FIG. 7, ground pin 340 includes lip 162 and beveled distal tip 164. Lip 162 of ground pin 340 comprises a conductive material and has an outside diameter greater than aperture 372 such that ground pin 340 fits securely in aperture 372 thus establishing an electrical connection with ground plane 370. Ground pin 340 is shown above aperture 372 in ground plane 370 prior to inserting ground pin 340 into ground plane 370. FIG. 8 shows ground pin 340 electrically coupled to ground plane 370 through lip 162.

FIG. 9 illustrates a magnified cross-sectional view of ground pin seated in or coupled to ground plane 370. Referring to FIG. 9, ground pin 340 is seated on component pad 345 that contacts liner 349 disposed through ground plane 370. Component pad 345 typically comprises a metal such as nickel plated with gold. Liner 349 is, for example, a plated material such as a conductive material of gold, aluminum, or other suitable material.

While ground pins 340 are electrically connected to ground plane 370, ground pins 340 are not electrically connected to power plane 360. Referring to FIG. 5, ground pins 340 are placed through apertures 520 in power plane 360. Apertures 520 in power plane 360 for ground pins 340 have an increased diameter that prevent ground pins 340 from contacting power plane 360. For a ground pin, such as ground pin 340, having an outside diameter of 0.65 mm. One example of an increased diameter of an aperture such as aperture 379, illustrated respectively in FIG. 9 is about 42 mils±2 mils. Aperture 379 is an opening or via (formed, for instance, by an etching process during the fabrication of PCB 320) of a diameter larger than the outside diameter of ground pin 340 such that the clearance in power plane 360 prevents ground pin 340 from connecting with power plane 360. Alternatively, an aperture may have a diameter larger than the outside diameter of ground pin 340, with a dielectric material such as a polyimide selectively introduced along the edges of the aperture such that ground pin 340 is not electrically connected to power plane 360. The amount of dielectric material may be that amount that prevents ground pin 340 from connecting with power plane 360 but still allows a sufficient diameter for ground pin 340 to be inserted therethrough. FIG. 5 also shows power pin 350 extending through and not contacting ground plane 370 through the use of an increased diameter such as aperture 379 that exists in ground plane 370.

FIG. 6 shows power pins 350 extending therethrough electrically connected to power plane 360. In this illustration, power pins 350 are not electrically connected to ground plane 370. Power pins 350 are inserted through apertures 510 in ground plane 370 having a diameter large enough so that power pins 350 do not electrically contact ground plane 370. Apertures 510 of ground plane 370 may have about the same or similar dimensions as apertures 520 in power plane 360. Additionally, though not shown, signal pins have apertures formed for both power plane 360 and ground plane 370.

FIG. 10 illustrates a top perspective view of an embodiment of a portion of PCB 320 of test contactor 305. As illustrated, ground pins 340 are disposed through apertures 520 located in power plane 360 that prevent ground pins 340 from contacting power plane 360. Similarly, power pins 350 are disposed through apertures 510 located in ground plane 370 that prevent power pins 350 from contacting ground plane 370. In FIG. 10, ghost lines used in apertures 510 represent apertures 510 as not being located on the same plane as apertures 520.

As previously mentioned, to further improve the decoupling performance due to the capacitance contribution between power and ground planes (360, 370), that define PCB 320 attached to test contactor housing 310 of test contactor 305, one or more capacitors are placed on the PCB. FIG. 11 illustrates a top perspective view of PCB 320 showing device footprint area 322. Additionally, PCB 320 includes four capacitor pads 610 configured to hold capacitors, e.g., 20 surface mount technology (SMT) capacitors, placed on the periphery of PCB 320 that is attached to test contactor housing 310. In one embodiment, each capacitor pad 610 includes at least one ground pad 362 and at least one power pad 364. In another embodiment, each capacitor pad 610 includes ground pad 362 located between two power pads 364. In yet another embodiment, each capacitor pad 610 may include a plurality of ground pads 362 and a plurality of power pads 364.

In one embodiment, power pad 364 provides a path that links the power terminal of the SMT capacitor to power plane 360 through conductive via 355 in aperture 525 shown in FIG. 12 (a magnified cross-section of a portion of PCB 320). Power pad 364 is connected to power plane 360 through conductive via 355. In contrast, ground pad 362 shorts the ground terminal of the SMT capacitor to ground plane 370. Ground pad 362 is connected to ground plane 370 through conductive via 345.

FIG. 12 further illustrates a cross-sectional view of capacitors located on PCB 420. Capacitors 630 and 640, arranged in parallel in one embodiment, act as a charge reservoir to react to any sudden demand of current from the electronic device being tested. In this configuration, capacitors 630 and 640 reduce the variations that occur from an external power source.

FIG. 13 illustrates a top perspective enlarged view of one capacitor pad 610 on PCB 320 coupled to test contactor housing 310. Capacitors 630 and 640 are shown to be coupled to ground pad 362 and to power pad 364 through conductive vias 345 and 355, respectively.

FIG. 14 illustrates a flow diagram for an embodiment of a test contactor such as described. At block 900, an integrated circuit having a set of contact points is positioned above a test contactor. At block 910, the loadboard contacts both the tester and the plurality of pins (e.g., ground pins, power pins, and signal pins) disposed in the test contactor housing. Embedded into the test contactor are the power and ground planes of the PCB. Additionally, SMT capacitors are located on the periphery of the PCB. At block 920, the plurality of pins of the test contactor housing contact the set of contact points of the electronic device. At block 930, the integrated circuit is tested.

Given the description provided above, studies show that the test contactor has improved performance over conventional test contactors. For example, in one study, the test contactor achieved higher capacitance than conventional test contactors as illustrated in Table 1. Higher capacitance is desirable for both the power and ground pin configurations so there is sufficient voltage for each pin when signaled. In this study, a three dimensional parameter extractor commercially available from Ansoft Corporation located in Pittsburgh, Pa. was used to extract inductive resistance capacitance (LRC) parasitic (mutual coupling from neighboring pins) of the test contactor in comparison with a conventional test contactor. Extractions were performed for two different power-ground pin configurations of each type of test contactor consisting of eight power pins and eight ground pins. The field solver extraction provided 8×8 IRC matrices for each power pin and ground pin configuration.

Referring to Table 1, the capacitance of the test contactor is much higher compared to conventional test contactors. For example, the test contactor of the claimed invention has 8.7×10⁻¹³ farads (F) compared to the capacitance 5.3×10⁻¹³ F of the conventional test contactor.

TABLE 1 Equivalent Per Pin IRC Parasitic of A Conventional Test Contactor and A Test Contactor Leffective Reffective Power pin/ Cself(Self (effective (effective ground pin capacitance inductance resistance Type Configuration in farads) in henrys) in ohms) Conventional Interdigitated 5.30E-13 1.39E-09 1.22E-02 test contactor Side 2.00E-13 4.581E-09 2.09E-02 Test contactor Interdigitated 8.70E-13 1.41E-09 1.38E-02 implementing techniques of the invention Side 6.60E-13 4.564E-09 2.57E-02

In the specification, the invention is described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. 

1. An apparatus comprising: a circuit substrate having a plurality of contactor pins extending between two opposing surfaces; at least one capacitor mounted on one of the two opposing surfaces of the circuit substrate, wherein the circuit substrate comprises a first layer of conductive material in a first distribution plane and a second layer of conductive material in a different second distribution plane, and respective ones of the plurality of contactor pins are coupled to one of the first layer and the second layer exclusive of the other.
 2. The apparatus of claim 1, wherein the at least one capacitor comprises a first contact point and a second contact point and the circuit substrate comprises a first conductive via coupled to the first distribution layer and a second conductive via coupled to the second distribution layer, and the first contact point of the capacitor is coupled to the first conductive via and the second contact point is coupled to the second conductive via.
 3. The apparatus of claim 1, further comprising a plurality of capacitors mounted on a surface of the circuit substrate. 